Volume Specific Heat Research Articles

Effects of Cover Crop on Selected Abiotic and Biotic Soil Health Indicators

Current cropping systems, like cover cropping, aim to improve soil health and crop productivity, with the former a more sustainable route to the latter. This can be done by evaluating the influence of cover crops (CCs) on soil health indicators, both abiotic and biotic, as is the objective of this study. Several CCs (crimson clover [Trifolium incarnatum L.], oats [Avena sativa], hairy vetch [Vicia villosa Roth.], winter wheat [Triticum aestivum L.], winter peas [Lathyrus hirsutus L.], flax [Linum usitassimum L.], triticale [Triticale hexaploide Lart.], cereal rye [Secale cereale], and barley [Hordeum vulgare L.]) were used across two research sites, set up using a completely randomized design with two levels of CCs (CC vs no cover crop [NC]) and three replicates during 2023. Soil samples were collected at 0-10, 10-20, and 20-30 cm depths and analyzed for soil physico-chemical properties and microbial biomass and composition. Results showed significantly lower bulk density values, greater water content (at 0 kPa soil water matric potential), greater volume-specific heat capacity (at 0 and -33 kPa soil water matric potential), greater total nitrogen, and numerically greater soil organic carbon under CC compared with NC management. This led to numerically greater microbial biomass and community composition (e.g., arbuscular mycorrhizal fungi, gram-negative and gram-positive bacteria, eukaryotes, and fungi), and slightly lower microbial stress indicators (genotypic and chemical structure categorizations) under CC compared with NC management. However, the lack of significant differences between treatments suggests that three years is insufficient to detect improvements in measured soil health indicators. Further, the significant differences in measured soil health indicators between study sites suggests an influence of soil texture and order, and this warrants further investigations.

Breaking the limitation of thermodynamic cycle efficiency of the plasma synthetic jet actuator: Noble gases

The low thermodynamic cycle efficiency of the plasma synthetic jet actuator (PSJA) limits its application in flow control of supersonic aircraft. To improve the thermodynamic cycle efficiency of the PSJA, the energy conversion process of the PSJA under single discharge has been investigated by thermodynamic theory analysis and numerical simulation. The relations between thermodynamic cycle efficiency, specific heat ratio of gas medium, non-dimensional energy deposition and heating efficiency are established by theoretical deduction. Employing the three-dimensional nonconstant electrode center energy deposition model, energy conversion processes in the PSJA with six different gas mediums have been investigated. The simulation results show that the thermodynamic cycle efficiency of the PSJA with noble gas medium can exceed 3.2 %, which is 1.92 times of the PSJA with air medium due to their low volume specific heat. The maximum jet x-velocity of helium can reach 493.11 m/s, which is 3.3 times higher than that of air. Consequently, noble gases prove to be effective in improving the thermodynamic cycle efficiency of the PSJA and enhancing the strength of the synthetic jet. The advancement in the performance of the PSJA contributes to their enhanced capabilities in the field of active flow control.

Application and thermal field analysis of multilayer thermal insulation in in-situ forming process of thermoplastic composites

The carbon fiber reinforced polyetheretherketone (CF/PEEK) composite material can achieve high efficiency and integrated assembly molding through in-situ consolidation, suitable for the preparation of high-speed motor rotor sleeves. However, the high forming temperature of CF/PEEK may cause demagnetization of the magnet once the temperature exceeds the curie temperature of the magnet. To address the insulation issues during the sleeve forming process, this study proposes using metal-containing multilayer thermal insulations (MTI) to prepare the insulation layer, which takes advantage of the heat transfer within the metal layer to achieve thickness-wise insulation. A finite element heat field model is established to analyze the effect of material thermal properties, layer structure, and thermal field conditions on the thermal insulation effect. The response surface methodology analysis shows that metal materials with high thermal conductivity and high volume-specific heat have better insulation performance. The highest temperature of the bottom surface of the copper-containing MTI is only 64% of that of the glass fiber reinforced polypropylene (GF/PP) layer MTI. Analysis of the layer structure shows that the closer the metal layer is to the heat source, the better the insulation effect. The sensitivity analysis of the thermal field conditions shows that the thermal conductivity of the inner layer has a greater impact on the insulation effect. Subsequently, the MTI containing copper was optimized in response to the specific insulation requirements of the motor rotor sleeve, providing a reference for the application of in-situ consolidated integrated assembly molding in thermoplastic composites.

Investigation of aerodynamics in combustion of vegetative waste on isothermal models

Modern agricultural vehicles contain a large number of components, which include micro Abstract. Conventional furnaces using alternative fuels, such as vegetable waste (VW), are widely used instead of furnaces operating on conventional fuels. The furnaces aggregated with dryers of SZT and SP type are widely used in agriculture and food industry. Two models with a suspended bed were investigated: with flare-vortex and cyclone-vortex modes. The first model assumes the presence of an inclined grate in a rectangular chamber with a concentrated supply of secondary blast, primary blast with material is supplied above the grate in its lower part, and the second model assumes a cylindrical-shaped chamber with primary air inlet in the center and cyclonic secondary blast inlet at a certain height. This scheme is close to the first, only in the lower part of the model concentrated input of primary blast with material. The methodology of aerodynamics studies included: feeding of material from the hopper; material cutoff after steady-state mode; collection and weighing of fallen particles from the model; determination of the time of material presence in the model by labeled particles. Modeling of aerodynamics for different schemes of furnace process organization showed the possibility of creating two-span or single-span furnace blocks depending on the required operating mode. The results of comparative studies of aerodynamics of flare-vortex and cyclone-vortex modes are given. The results of comparative studies of aerodynamics of flare-vortex and cyclone-vortex modes are given. Optimal blowing parameters, secondary and primary air ratio, furnace design parameters contributing to the maximum specific volume heat stress are determined.

Thermal conductivity and specific volume heat capacity of bentonite–fly ash-based fluidized thermal backfill

Thermal conductivity and specific volume heat capacity of bentonite–fly ash-based fluidized thermal backfill

Effect of water on CO2 absorption by a novel anhydrous biphasic absorbent: Phase change behavior, absorption performance, reaction heat, and absorption mechanism

The ionic liquids (ILs)-based biphasic absorbents are viewed as promising substitutes for CO2 capture due to their remarkable CO2 absorption performance, excellent stability and low energy requirement for regeneration. Further decreasing the regeneration heat requirement can be achieved by utilizing ILs-based anhydrous biphasic absorbents, whose solid CO2-rich phase contained small volume and low specific heat capacity. Given the high hygroscopicity of ILs and the water present in the flue gas, comprehending the effect of water is crucial for post-combustion carbon capture using ILs-based anhydrous biphasic absorbents. In this work, the effect of water on CO2 absorption by an anhydrous biphasic absorbent, tetramethylammonium glycinate ([N1111][Gly])/ethanol, was studied. The experimental results demonstrated that the CO2 loading and absorption rate were decreased in the presence of water, but the CO2 desorption efficiency was enhanced. Besides, the presence of water slightly reduced the reaction heat of CO2 absorption by [N1111][Gly]/ethanol to 69.48 kJ/mol CO2, which was 20% lower than that of monoethanolamine (MEA) absorbent. Furthermore, the 13C NMR results indicated that the primary CO2-product was bicarbonate in the presence of water rather than carbamate. There were three possible pathways for bicarbonate generation: zwitterion hydrolysis, carbamate hydrolysis, and base-catalyzed CO2 hydration. Water and ethanol competed to react with carbamate. When a large amount of water was present (≥70 wt%), the reaction of ethanol with the carbamate hardly occurred.

First-Principles Study of the Structural, Mechanical and Thermodynamic Properties of Al11RE3 in Aluminum Alloys

The stability and mechanical and thermodynamic properties of Al11RE3 intermetallics (RE = Sc, Y and lanthanide La-Lu) have been investigated by combining first-principles and Debye model calculations. It was found that the formation enthalpies of the Al11RE3 intermetallics are all negative, indicating that they are stable; moreover, the experimental values of Al11La3 and Al11Ce3 are in good agreement with the predicted values, which are −0.40 kJ/mol and −0.38 kJ/mol, respectively. The calculated results of the mechanical properties reveal that the Young’s modulus E and shear modulus G of Al11RE3 (RE = La, Ce, Pr, Nd and Sm) intermetallics are obviously greater than that of Al, implying that the stiffness, toughness, and tensile strength of them are significantly greater than those of aluminum, and that they, as strengthen phases, can effectively improve the mechanical property of aluminum alloys. The Poisson’s ratio v of Al11Sc3 (0.37) is the largest, and the heterogeneity is obvious. All the Al11RE3 intermetallics can enhance the thermostability of the aluminum because of their lower Gibbs free energy F in the range of −5.002~−4.137 eV/atom and thermal expansion coefficient α of Al in the range of 2.34~2.89 × 10−5/K at 300K, as well as higher entropy and constant volume-specific heat than aluminum at finite temperatures. With an increase in the atomic number, different change trends were observed for the formation enthalpy ΔHf, bulk modulus B, Young’s modulus E, and shear modulus G. This paper can provide ideas and help for designing a high-performance, heat-resistant aluminum alloy.

Study on Calculation Method of Heat Exchange Capacity and Thermal Properties of Buried Pipes in the Fractured Rock Mass-Taking a Project in Carbonate Rock Area as an Example

Fractures are developed in carbonate rock areas, and the fracture water flow significantly influences the heat exchange between buried pipes and the rock mass by induing heat convection, providing the carbonate rock area a strong heat exchange capacity and preferable conditions for shallow geothermal development and utilization. In this paper, the calculation method of heat exchange capacity of buried pipes based on fracture distribution characteristics is proposed and deduced, featuring such advantages as quick speed and low cost. Taking an actual project in carbonate rock area as an example, the heat exchange capacity of buried pipes was obtained by the following two methods: in-situ thermal response test and calculation based on fracture distribution characteristics. In the thermal response test, the initial ground temperatures of the two test holes were 15.18 °C and 12.72 °C. By fitting the linear equation of time and average temperature with a linear thermal source model, the heat exchange capacities were 57.21 W/m and 58.22 W/m, the thermal conductivities were 3.56 W/(m·K) and 2.32 W/(m·K), the thermal diffusivities were 1.71 × 10−6 m2/s and 1.12 × 10−6 m2/s, and the volume specific heat capacity was 2.08 × 106 J (m3·K). The test results indicated that the thermal property parameters of rock and soil mass were higher than those of other areas, with obvious wide-range distribution characteristics. Through the statistical analysis of outcrop fracture characteristics, combined with the cube law to calculate the fracture water flow and convective heat transfer, an alternative method for the calculation and optimization of buried pipe heat transfer in fractured rock mass area is also proposed in this paper. According to the measured fracture distribution characteristics of the field outcrop, the heat exchange capacities of the two holes were 57.26 W/m and 58.56 W/m, which were basically consistent with the thermal response test values and verified the reliability of the calculation method of heat exchange capacity of buried pipes based on fracture distribution characteristics.

Numerical Study on Heat Transfer and Performance of Seasonal Borehole Thermal Energy Storage

Design of the borehole thermal energy storage (BTES) is very important for the seasonal solar thermal storage system. The BTES designed based on the empirical method could lead to some unsatisfied effects in actual operations. This paper simulated the BTES operation in one year to study the effects of soil thermal conductivity, soil volume-specific heat, initial soil temperature and relative surface area of storage on energy efficiency of the BTES. The results show that energy efficiency of the BTES reaches the maximum when soil thermal conductivity is 1.8 W/(m·K). According to the results, soil thermal conductivity has more significant effects on the heat extraction per soil volume but has the most negligible impact on energy efficiency of the BTES. At the same time, relative surface area of storage is the most influential factor on energy efficiency of the BTES. Finally, a new BTES design method was proposed which is suitable for the studied parameter range. It is worth noting that the present study focuses on the continuous operation of the system and fixed buried pipe spacing, while the intermittent operation and other buried pipe spacing will be studied in future work.

Cohesive and Thermal Properties of Sodium Cyanide-Halide Mixed Crystals

In order to analyse the cohesive and thermal properties of sodium cyanide-halide mixed crystals an Extended Three Body Force Shell Model (ETSM) has been applied by incorporating the effect of translational-rotational (TR) coupling. We have conducted theoretical research on cohesive and thermal properties, such as cohesive energy (, molecular force constant (f), compressibility (), Restrahlen frequency (, Debye temperature (D), Gruneisen parameter (), Moelwyn Hughes constants (F1) and the ratio of volume thermal expansion coefficient (v) to volume specific heat (Cv), as a function of temperature within the temperature range 50K T 300K at concentration x=0, 0.27, 0.58 and 1. The current model computations and the findings of the available experiments are in good agreement. The ETSM is a sufficiently realistic model and may be applied to a variety of other mixed crystals in this family.

Low-Temperature Performance of Asphalt Mixtures Modified by Microencapsulated Phase Change Materials with Various Graphene Contents

Microencapsulated phase change materials (PCMs) added to conventional ones can store excessive heat energy and reduce thermal stresses. In this study, melamine–formaldehyde resin phase change microencapsulated PCMs, with different contents of graphene (CG), were added to asphalt mixtures, in order to reduce their low-temperature cracking, induced by thermal stresses. Low-temperature and heat-conducting/storing performance of the obtained mixtures was examined via beam bending tests, semi-circular bending low-temperature performance tests, thermal conductivity tests and volume-specific heat capacity tests. Besides, the prepared asphalt mixtures’ water stability and high-temperature stability values were obtained via freeze-thaw splitting and wheel tracking tests. The low-temperature performance of PCM-modified asphalt mixtures was evaluated via their bending strain energy densities, with one of the PCM-modified asphalt mixtures, namely CGMFPCM3, synthesized by the authors, was 1.7 times higher than that of the common asphalt mixture. Although the dynamic stability of all three PCM-modified mixtures was deteriorated by 68, 50, and 20% compared to the common one, that of CGMFPCM3 still complied with the standard requirement. Thermal conductivity and volume-specific heat capacity of the asphalt mixture at 278.15 K was enhanced by 5 and 43%, respectively, after adding CGMFPCM3. It is recommended for reducing the temperature variation-induced cracking in the asphalt pavement. Thermal conductivity and volume-specific heat capacity can be used for evaluating the temperature-regulating performance of asphalt mixtures.

Monolayer XN2 (X[dbnd]Ti, Zr, Hf): Novel 2D materials with high stability, simultaneously high electron and hole mobilities from density functional theory

2D nitrides have attracted extensive attention because of their novel photoelectric properties and wide applications. In this work, we propose three novel 2D nitride materials, namely TiN2, ZrN2 and HfN2, and further systematically studied their stability, elastic property, electronic structure and thermal conductivity. The results show that the proposed monolayer XN2 (XTi, Zr, Hf) have high mechanical and dynamic stabilities. Furthermore, the monolayers are all direct bandgap semiconductors with band gaps of 1.87 eV, 2.00 eV and 2.69 eV, respectively. Based on deformation potential theory, it is found that the monolayers simultaneously have high hole and electron mobility at room temperature, up to 104–105 cm2 V−1 s−1. Also, due to the high group velocity and phonon lifetime, as well as volume specific heat capacity, monolayer XN2 (XTi, Zr, Hf) show high lattice thermal conductivity, as high as 41.80 W/m K, 60.22 W/m K and 56.88 W/m K, respectively. All these characteristics indicate that the proposed monolayer XN2 (XTi, Zr, Hf) have the potential to be applied in the fields of high-mobility polar semiconductors and photovoltaic devices in the future.

Effect of protein content on the thermal effusivity of foods

Abstract The availability of thermophysical properties of both foods and their constituents is of considerable importance to the industry. The thermal effusivity is one of the less explored thermophysical parameters. It governs the penetration of heat into materials and is defined as the square root of the product of thermal conductivity of the material, volume-specific heat capacity, and density. This paper describes the application of a relatively new inverse photopyroelectric method (IPPE) to determine thermal effusivity of dehydrated whey protein isolate and egg white powder versus protein content. In both cases the effusivity values decreased linearly with increasing protein content. One percent increase in protein content of whey protein isolate and egg white lead to 6.5 and 7.2 Ws1/2 m−2 K−1 decrease in effusivity values, respectively.

A comparative ab initio study of the mechanical, dynamical and thermophysical characteristics of XC2 (X = La, Ce, Tb, Ho)

The structural, mechanical, lattice dynamics and thermophysical characteristics of XC2 (X = La, Ce, Tb, Ho) have been theoretically investigate by means of density functional theory (DFT). The optimized lattice constants and elastic constants of XC2 (X = La, Ce, Tb, Ho) are in an excellent agreement with the available experimental data. The elastic moduli including elastic constants Cij, bulk modulus B, shear modulus G, Young's modulus E, Debye temperature θ, wave velocities and anisotropy indexes have been predicted successfully. The brittle/ductile properties of four compounds are determined by the ratio of B/G. According to the values of anisotropic indexes, three dimensional (3D) surface constructions indicate that XC2 shows mechanical anisotropy. Results indicate that four compounds can be stabilized mechanically and dynamically in the ground state phase of the tetragonal structure. The thermophysical characteristics such as internal energy, Helmholtz free energy, entropy and the constant volume specific heat under high temperatures are also predicted and analyzed comprehensively based on phonon density of states.

Thermodynamic instability of 3D Einstein-Born-Infeld AdS black holes * *Supported in part by the National Natural Science Foundation of China (11005016, 11875196, 11375121)

Super-entropic black holes possess finite-area but noncompact event horizons and violate the reverse isoperimetric inequality. It has been conjectured that such black holes always have negative specific heat at constant volume or negative specific heat at constant pressure whenever , making them unstable in extended thermodynamics. In this paper, we describe a test of this instability conjecture with a family of nonlinear electrodynamic black holes, namely 3D Einstein-Born-Infeld (EBI) AdS black holes. Our results show that when nonlinear electrodynamics effects are weak, the instability conjecture is valid. However, the conjecture can be violated in some parameter region when nonlinear electrodynamics effects are strong enough. This observation thus provides a counter example to the instability conjecture, which suggests that super-entropic black holes may be thermodynamically stable.

Analytical solution of heat transfer performance of pin-array stack regenerator in stirling cycle

Regenerators play an important role in Stirling engines, pin-array stack regenerators have low flow resistance, to verify their advantages in Stirling engines, the heat transfer performance was explored theoretically, and the equivalent heat transfer coefficient and its influencing factors were obtained. The results show that the magnitude of equivalent heat transfer coefficient of this kind of regenerator can be up to 105W/m2·K, indicating that the pin-array stack generator is satisfactory when used in Stirling engines. Equivalent heat transfer coefficient is influenced by three factors: the working frequency, radius and thermal diffusivity of pins. With the increase of frequencies, the heat transfer performance increase monotonously, while with the increase of radius, there are two extreme points. Based on this, two typical working conditions are determined, the thermally penetrated condition and the thermally unpenetrated condition, and the heat transfer performance of the thermally penetrated condition is good, but the thermally unpenetrated condition should be avoided. Based on the equivalent heat transfer coefficient, the regenerator size optimization criterion was proposed according to the target parameter of specific volume heat transfer capacity, and the optimal parameters can be obtained by setting the relative radius to be 1.

Mathematical and physical modeling of FE-SEM surface quality surrounded by the plasma channel within Al powder-mixed electrical discharge machining of Ti-6Al-4V

Electrical discharge machining (EDM) is known as one of the well-defined advanced manufacturing techniques. The electro-thermal property of EDM enables us to capture the electrical and thermal changes within the plasma channel. Our research has studied the impact of the electro-thermal of the plasma channel on surface integrity. We have analyzed the changes in the plasma channel by considering its physical characteristics based on the EDM’s input parameters such as discharge current (I), pulse-on time (Ton), and concentration of added Al powder (Cp). In our experiment, adding Al powder decreased the dielectric resistance of kerosene. Furthermore, our mathematical and physical model demonstrated that adding powder had a positive effect up to 2.5 g/l. Moreover, the uneven distribution of powders into dielectric caused unstable discharge on the surface. We also studied the defects and changes of the plasma channel’s features by using field emission scanning electron microscopy (FE-SEM). The consequence of the plasma channel changes led to the crack’s disappearance entirely when the Al powder was used. It should be noted that with Ti-6Al-4V, it is hard to machine material, which is usually due to low thermal conductivity and its volume-specific heat. In our study, the fast-cooling rate created a diffusionless acicular martensitic microstructure, which led to a distorted hexagonal close-packed (HCP) crystal structure with the designation α′. This occurred while a high rate of quenching martensitic α′ was formed. The plasma channel creates a recast layer, which was affected by metallurgical changes within the EDM process. By using electron dispersive scanning (EDS) method and elemental mapping, we observed that the cross-section of the workpiece in the HAZ area led to the optimized oxidization, carbonization, and degree of fragility on the surface. Moreover, as the rate of the current intensity increased from 15 to 20-25A, the machining time improved by 16%, 12%, and 7%, respectively. Our experiment is consistent with our proposed mathematical model, and it can have practical applications, especially in medical, aerospace, and automobile industries. To the best of knowledge, our mathematical model that we have proposed for our experiment detects appearance and disappearance of metallurgical defects.

Insight into the phase transition, elastic and thermodynamic properties of BeS compound under high pressure and temperature from the first principle calculation

Based on the first principle plane wave pseudopotential and generalized gradient approximation (GGA) method, the phase, elastic and thermodynamic properties of BeS compound at pressure ranging from 0 to 175 GPa are calculated. After studying the energy-volume and entropy difference-pressure of the zinc blende, NiAs, NaCl and CsCl structures of BeS compound in depth, we consider the zinc blende and NiAs structures as two stable structures for BeS compound. The phonon spectra and elastic constants reveal that zinc blende and NiAs structures are also structurally and mechanically stable at ambient conditions. Furthermore, the phase transition pressure from zinc blende structure to NiAs structure is 58.615 GPa. Intriguingly, the anisotropies of the elastic and sound velocities of BeS are found to exhibit anisotropic characteristics, which is the first comprehensive study on the mechanical properties of BeS compound. Notably, we report for the first time the thermodynamic properties of NiAs structure, such as the Debye temperature, specific volume heat capacity, which shows great potential in the further study on the properties of BeS compound.

An frequency domain analysis method of thermal parameters unsteady-state detection of building wall

ABSTRACT The in-situ inspection technology of thermal properties of building wall is an important technical guarantee to achieve the goal of building energy conservation. However, there is still a lack of fast, simple, and accurate unsteady-state detection method under natural conditions. This paper focuses on the thermal performance test and analysis method of building wall under natural condition. Two frequency domain analysis methods were developed for the thermal conductivity, as well as volume specific heat and thermal inertia of homogeneous wall along with the harmonic reaction method and the frequency domain analysis theory. The frequency response relationship between the internal and external surface temperature waves and indoor air temperature waves was established, and the relationship contains thermal performance parameters of wall. The thermal conductivity and specific volume heat of wall can be solved by using the response relation. Numerical simulation verification of the method was completed by using ANSYS software and the experimental verification by using wall insulation materials were accomplished in the laboratory. The maximum relative error of numerical simulation results is 1.48%, and that of laboratory experiment results is 8.75%. The implications of these results with respect to the influence on the in-situ inspection technology of building wall are discuss.

Heat generation quantification of high-specific-energy 21700 battery cell using average and variable specific heat capacities

The electrical performance, safety and life of a battery are closely related to its operating temperature; therefore, a thermal management system is necessary to ensure that the battery operates within its most suitable temperature range. Accurately testing the heat generation of a battery is necessary for the design of a thermal management system. Specific heat capacity is one of the most important parameters of thermophysical properties, and its accurate measurement is a prerequisite for the quantitative analysis of battery heat generation. In the literature on battery heat generation tests, the average specific heat capacity is usually used to calculate the battery heat generation. Thus, the change in the specific heat capacity of the battery is not considered. Considering the high-specific-energy 21700 battery made with a nickel-cobalt-manganese (NCM)/graphite material system, this paper compares for the first time the difference between using the average specific heat capacity and variable specific heat capacity to calculate the instantaneous heat generation of a battery. The experimental results showed that the specific heat capacity in the target temperature range during the actual use of power batteries (i.e., a low temperature range of 25–35 °C) had a more significant impact on the heat generation power calculation error, and the relative error could reach 30%. In addition, based on the obtained variable specific heat capacity, the heat generation characteristics of the 21700 battery under different operating conditions were analysed. The results showed that this battery has a higher specific volume heat generation power compared with the pouch-type batteries reported in the literature. This article provides guidance for battery cell thermal simulation, more accurate quantitative measurement of battery heat generation and thermal management system design.